Bendix Commercial Vehicle Systems VM-3 User Manual

®

Bendix® VM-3™ Firewall Manifold

DESCRIPTION

The VM-3™ is a control manifold serving as a manifold unit
for air passages between cab and engine compartment and
housing a double check valve and PR-4
valve.

OPERATION

1. The double check valve receives supply air from the rear
(primary) supply system, through port No. 3 on Fig. 1,
and front (secondary) supply system, through port No.
1 on Fig. 1, and delivers whichever is higher in pressure
to the spring brake system and through another port to
the trailer supply through the dash mounted PP-7™ tractor
protection control valve.

2. The PR-4™ pressure protection valve receives supply air
from the front (secondary) supply port and supplies
protected air to three ports, one on the engine side and
two on the cab side. The PR-4™ valve will deliver air to
these ports only after the front supply system has built
up to at least 60 psi.

3. Supply air for the trailer control hand valve is taken from
a port inside the cab supplied from the rear (primary) air
supply.

The location and function of the various ports are shown in
Fig. 1 for the engine side of the VM-3™ manifold and in Fig.
2 for the cab side. The chart shown on Fig. 1 explains the
purpose and function of each port on the engine side and
the chart shown on Fig. 2 the cab side.

WARNING! PLEASE READ AND FOLLOW
THESE INSTRUCTIONS TO AVOID
PERSONAL INJURY OR DEATH:

When working on or around a vehicle, the following
general precautions should be observed at all times.

1. Park the vehicle on a level surface, apply the

parking brakes, and always block the wheels.
Always wear safety glasses.

2. Stop the engine and remove ignition key when

working under or around the vehicle. When
working in the engine compartment, the engine
should be shut off and the ignition key should be

™

pressure protection

SD-03-3410

NO.3

NO.9

NO.2

NO.8

NO.7

NO.6

NO.5

FIGURE 1 - ENGINE SIDE

removed. Where circumstances require that the
engine be in operation, EXTREME CAUTION should
be used to prevent personal injury resulting from
contact with moving, rotating, leaking, heated or
electrically charged components.

3. Do not attempt to install, remove, disassemble or
assemble a component until you have read and
thoroughly understand the recommended
procedures. Use only the proper tools and observe
all precautions pertaining to use of those tools.

4. If the work is being performed on the vehicle’s air
brake system, or any auxiliary pressurized air
systems, make certain to drain the air pressure from
all reservoirs before beginning ANY work on the
vehicle. If the vehicle is equipped with an AD-IS
air dryer system or a dryer reservoir module, be
sure to drain the purge reservoir.

5. Following the vehicle manufacturer’s
recommended procedures, deactivate the electrical
system in a manner that safely removes all
electrical power from the vehicle.

6. Never exceed manufacturer’s recommended
pressures.

7. Never connect or disconnect a hose or line
containing pressure; it may whip. Never remove a
component or plug unless you are certain all
system pressure has been depleted.

NO.4

NO.1

™

1

NO.8

NO.9

NO.3

NO.2

NO.4

NO.1

1234

5

67

8

NO.7

NO.6

NO.5

ENGINE SIDE FIGURE 1

Port Ident. on

No. Casting Function

1 Frt. Sup. Supply from No. 2 circuit reservoir.

Blue

2 Park Sup. Delivers air from double check valve

Red area to spring brake relay valve (R-8).

3 Rear Sup. Supply from No. 1 circuit reservoir.

Green

4 Rad. Fan Delivers protected air supply from

Blk. PR-4 valve. Suggested use - air

operated fan clutch.

5 Diff. Lock Connects directly to port No. 9 (Fig.

Blk. 2) in cab. Suggested use - manifold

connection to differential lockout
mechanism. This is a 90

0

pass-through

passage.

6 Trl. Sup. Connects directly to port No. 10 in

Yel. cab. Suggested use - deliver air from

trailer supply valve (such as BW PP-7)
to trailer. This is a 90° pass-through
passage.

7 (None) Connects directly to port No. 11 in

cab. Suggested use - any auxiliary
manifold function. This is a straight
through passage.

8 Air Rest. Connects directly to port No. 12 in

Blk. cab. Suggested use - air cleaner

restriction gauge. This is a straight
through passage.

9 Prk. Del. Connects directly to port No. 8 (Fig.

Red 2) in cab. Suggested use - deliver air

from park control valve to spring
brake control valve (SR-1™ valve).
This is a straight-through passage.

10 Spg. Brk. Connects to secondary circuit reservoir

Rest. - Grn. and to port No. 4 (Fig. 2) in cab.

Suggested use - supplies secondary
reservoir air to the balance port of the
SR-1 spring brake control valve.

910

11 12

CAB BULKHEAD SIDE FIGURE 2

Port Ident. on

No. Casting Function

1 Frt. Gauge Connects to gauge for No. 2 circuit

Blue reservoir.

2 Prk. Sup. Supplies air from double check valve

Red to park control valve.

3 Rear Gauge Connects to gauge for No. 1 circuit

Green reservoir.

4 Hand Brake Supplies air from No. 2 circuit reservoir

Supply to trailer hand control valve in
Green cab. Connects with No. 10 on engine

5 Access Supplies protected air from PR-4

side.

Blk. to any accessory control in cab.

6 Access Supplies protected air from PR-4

™

valve

™

valve

Blk. to any accessory control in cab.

7 Trl. Sup. Supplies air from double check valve

Red to trailer supply valve (tractor

protection).

8 Prk. Del. Receives air from delivery of park

Red control valve to deliver to SR-1

™

spring
brake control valve. Connects with No.
9 on engine side.

9 Diff. Lock Receives air from delivery of differen-

tial lockout control valve. Connects
with No. 5 on engine side.

10 Trl. Del. Receives air from trailer supply valve

(tractor protection) to supply trailer.
Connects to No. 6 on engine side.

11 (None) Auxiliary manifold for any accessory

function connects to No. 7 on engine
side.

12 Air Rest. Suggested use - air cleaner restriction

Blk. gauge. Connects with No. 8 on engine

side.

2